An electrolysis unit for obtaining a gaseous product

Abstract

The present invention relates to an electrolysis unit, wherein a fluid manifold system delivers electrolyte to and expels electrolyte from an electrolysis cell, a cavity of an expandable closure means is pressurized, causing its shell to expand and increasing the volume of the cavity, and the expandable closure means is disposed within the fluid manifold system, such that when the expandable closure means is in a depressurized state, the fluid manifold system is open to the passage of electrolyte, and when the expandable closure means is in a pressurized state, the fluid manifold system is closed to the passage of electrolyte.

Description

[Technical field]

[0001] The present invention relates to an electrolysis unit in which an electrolyte (such as water or brine) is electrolyzed to obtain gaseous products such as oxygen, hydrogen, chlorine, etc. Furthermore, the present invention relates to a method in which water is electrolyzed to obtain oxygen and hydrogen. [Background technology]

[0002] The production of hydrogen and oxygen by electrolysis of aqueous solutions is a well-known technique. In the past, techniques based on the electrolysis of acidic or alkaline solutions have been used, the latter due to the less aggressive nature of the electrolyte, which provides a wider range of metallic materials for their production.

[0003] Electrolysers can be advantageously used with renewable energy sources such as solar power. Solar power is used to generate the electrical current that must be applied to the electrolyser to separate water into its components hydrogen and oxygen. In such configurations, the electrolyser needs to be shut off at night, when renewable solar energy is not available.

[0004] During this period, when the polarization is switched off, the anode and cathode coatings are not protected and can be damaged by reverse currents resulting from stray currents flowing in the drain manifold that hydraulically connects all the cells of the electrolyser.

[0005] JP5876811B2 describes a method for preventing reverse current for an ion exchange membrane electrolysis cell, which includes an anode chamber housing an anode, a cathode chamber housing a cathode, an anolyte supply manifold for supplying anolyte to the anode chamber, and a catholyte supply manifold for supplying catholyte to the cathode chamber. After the ion exchange membrane electrolysis cell is stopped, a low-conductivity material having a lower electrical conductivity than the anolyte or catholyte is poured into at least one of an anolyte supply pipe for supplying the anolyte from an anolyte tank to the anolyte supply manifold and a catholyte supply pipe for supplying the catholyte from the catholyte tank to the catholyte supply manifold.

[0006] The current state of the art uses a closure system with valves to seal each cell and avoid the possibility of stray currents.

[0007] In this context, JP-2020012146A describes a cut-off valve provided in the flow path to the electrode chamber of the electrolytic cell to prevent reverse current when the electrolysis unit is shut off.

[0008] This method requires that each individual cell be closed separately by a valve in front of each inlet, and therefore implementation for larger numbers of cells is complex and time consuming.

[0009] It is therefore an object of the present invention to provide a system and method using an improved closure structure to protect the anode and cathode coatings of the electrolyte in an electrolysis unit from damage due to stray currents when the electrolytic cell is shut off. Summary of the Invention

[0010] The aforementioned object is achieved by an electrolysis unit as defined in claim 1 and by a method for electrolysis as defined in claim 9. Advantageous configurations and developments are evident from the dependent claims.

[0011] According to a first aspect of the invention, an electrolysis unit includes a plurality of electrolysis cells, each having an anode, a cathode, and an ion exchange membrane dividing the electrolysis cell into an anode compartment and a cathode compartment. The unit also includes a fluid manifold system having fluid conduits for feeding electrolyte into and discharging electrolyte from the electrolysis cells. The unit further includes an expandable closure means having a liquid-tight shell surrounding a cavity, said liquid-tight shell having a pressure port. The unit also includes a pressure unit connected to the pressure port for pressurizing the cavity such that the liquid-tight shell expands and the volume of the cavity increases. The expandable closure means is disposed within the fluid manifold system, whereby when the expandable closure means is in a reduced pressure state, the fluid manifold system is open to the passage of electrolyte, and when the expandable closure means is in a pressurized state, the fluid manifold system is closed to the passage of electrolyte.

[0012] An electrolyte is fed to the anode or cathode chamber of the electrolysis cell via a fluid conduit, which provides an alkaline solution supply and drainage through a fluid conduit at the opposite side of the cell. An expandable closure means is placed inside such conduit prior to operation of the electrolysis cell. The expandable closure means has a pressure port that can be accessed via a hose connected to a pressure unit external to the system. During operation, i.e. when alkaline water electrolysis is performed, the expandable closure means is contracted, which corresponds to a reduced pressure state. This means that the cavity enclosed by the closure means is compressed by the surrounding electrolyte.

[0013] This arrangement of the expandable closure means has the advantage that stray currents are unlikely to form between the cells during the shut-off of the unit, avoiding reverse currents and thus avoiding damage to the coatings of the anodes and cathodes. The operating life of the unit is therefore extended and material and maintenance costs can be reduced. The expandable closure means has the advantage over the installation of simple valves that it can be easily controlled from the outside by activating the pressure unit. Depending on the arrangement of the expandable closure means, several conduits can be isolated simultaneously instead of all of them being closed individually by valves. This results in time savings and, moreover, no complex transformation of the electrolysis unit is necessary when switching it to active mode. The expandable closure means can be contracted simply by applying a reduced pressure. It is therefore easily possible to open and close the conduits at a fast frequency. This unit including the expandable closure means allows a process that is reversible and can be repeated many times.

[0014] According to another embodiment, the unit can be used for alkaline water electrolysis, where the alkaline water electrolyte is electrolyzed to obtain oxygen and hydrogen.

[0015] According to yet another configuration of the electrolysis unit, at least one fluid conduit provides a fluid connection from one electrolysis cell to another. Thus, an electrolysis unit built with several cells can be supplied via a common electrolyte manifold system.

[0016] According to one embodiment of the electrolysis unit, the expandable closure means is placed in at least one of the fluid conduits directly in front of the inlet of the electrolysis cell. In this case, in the pressurized or expanded state of the expandable closure means, there is thus no longer any connection between the cell in whose direct supply conduit the expandable closure means is placed and the neighboring conduits. In this way, the cell is protected from stray currents that could otherwise propagate through the electrolyte. Due to its simple design, the expandable closure means can be used spatially flexibly. By placing it in the direct supply conduit of the cell, it is possible to block only individual cells of the unit. For example, this can be beneficial during the shutdown of the unit or part of it.

[0017] By placing several expandable closure means directly in the supply conduit at each of the inlets of the individual cells, a closed system for the complete unit can be achieved, which allows individual isolation of these cells. Nevertheless, it is also possible for several closure means to be inflated or deflated simultaneously by connecting pressure hoses from the individual pressure ports of the expandable closure means to a pressure unit, for example a pressure pump.

[0018] According to another embodiment of the electrolysis unit, the fluid manifold system includes a main conduit from which at least one fluid conduit branches, and said expandable closure means is disposed in the main conduit.

[0019] For example, a main conduit may be located in a lower or downstream portion of the fluid manifold system of the electrolysis unit and deliver alkaline solution to the vicinity of the electrolysis unit, the main conduit feeding fluid conduits that branch off from the main conduit to individual cells electrically connected in series.

[0020] The expandable closure means may be pre-installed in the main conduit. Upon expansion, the expandable closure means expands completely into the main conduit of the unit and blocks all fluid conduits branching off from the main conduit to the electrolysis cells. Thus, the electrolyte supply of the entire unit can be blocked at once, instead of having to control the supply of each individual cell separately. In this way, all cells are isolated and therefore it is not possible for stray currents to form within the entire unit. This subsequently prevents the formation of reverse currents in the individual cells.

[0021] Placing a single expandable closure means in the main conduit can be advantageous when performing maintenance work. The individual cells are still completely independent from the installation of the expandable closure means. If the unit needs to be maintained, only one closure device is affected and only the main conduit is involved. This set-up is material-saving and therefore cost-saving and simplifies application by the user. One closure device for the complete unit is provided and is operated by inflating and deflating the expandable closure means placed in the main conduit.

[0022] The expandable closure means can be operated via an external gas supply system, for this purpose a pressure port is provided on the liquid-tight shell of the expandable closure means, which may be connected to a hose that leads out of the manifold system to a pressure unit.

[0023] The pressure unit can be applied to pump ambient air directly into the cavity of the expandable closure means through the supply system, or alternatively, the pressure unit can be connected to a tank containing nitrogen, which provides the system with the fluid needed to pressurize the expandable closure means.

[0024] Filling the cavity with readily available gases such as nitrogen or air is a cost-effective option. Furthermore, the filling and emptying process is uncomplicated, fast and error-resistant. In case of an accident or gas leak, no significant hazards are expected and therefore no additional safety measures are required.

[0025] According to one embodiment of the present invention, the expandable closure means includes a ballast component that holds the expandable closure to the bottom of the fluid manifold system when deflated.

[0026] In particular, the expandable closure means remains in the conduit permanently, i.e. during the electrolysis process. It is therefore important that the contracted expandable closure means does not disturb the electrolysis process. On the one hand, the depressurized expandable closure means should have a small volume and block only a small part of the cross-sectional area of ​​the conduit. On the other hand, the expandable closure means must not move in the fluid manifold system. This is particularly important when the expandable closure means is re-inflated. It must be ensured that the expandable closure means is still in the same place, for example placed directly in front of the fluid conduits branching off from the main conduit so that it can block these during re-inflation. Furthermore, in the depressurized state, floating of the expandable closure means inside the manifold, which could block the inlet opening, must be prevented. To ensure that the liquid-tight shell of the depressurized expandable closure means does not move in the conduit and cause undesirable positioning, a ballast component is used in this embodiment. In this way, the liquid-tight shell of the depressurized expandable closure means is attached to the lower wall of the fluid conduit and does not fold up. The ballast component is a metal rod inserted into a cavity in the expandable closure means, the length of which is slightly shorter than the expandable closure means so that it is housed within the expandable closure means.

[0027] Since the cross-sectional area of ​​the contracted expandable closure means is smaller than the inner cross-sectional area of ​​the conduit, the contracted expandable closure means will not normally interfere with the electrolysis process, however, the ballast component advantageously holds the contracted expandable closure means at the bottom of the conduit, thus providing an even better means for preventing any interference with the electrolysis process.

[0028] In another embodiment, the expandable closure means is fixed to the wall of the fluid conduit, for example to the lower part of the conduit, in particular the main conduit. When the contracted expandable closure means is attached along the wall of the fluid conduit, it cannot move freely and therefore does not interfere with the electrolysis process. Upon re-inflation, it is ensured that the expandable closure means is still in its position, for example directly in front of and blocking the fluid conduits that branch off from the conduit in which it is located, for example the main conduit. In this case, no additional ballast components are required.

[0029] In yet another embodiment of the present invention, at least a portion of the shell of the expandable closure means can be manufactured from a non-floating heavy material. In other words, the ballast components are distributed evenly throughout the shell of the expandable closure means. This has the advantage that there are no additional components in the expandable closure means, which saves space and is less prone to maintenance. Due to its weight, the expandable closure means will lower itself by gravity to the bottom of the fluid conduit when not inflated. In this case, no additional ballast components are required.

[0030] In yet another embodiment of the present invention, the fluid manifold system can have an integrated chamber in which the contracted expandable closure means is retracted and stored as long as the electrolysis process continues. This chamber can be located near the mounting location of the pressure port. When the pressure unit contracts, the expandable closure means can create a slight negative pressure. In this way, the expandable closure means can be retracted into the storage chamber and easily pushed out again from the storage chamber when expanded.

[0031] In one embodiment of the invention, the liquid tight shell of the expandable closure is an electrical insulator.

[0032] To effectively prevent stray currents, in this embodiment, not only a hydraulic barrier by separating the compartments containing the electrolyte, but also a current flow barrier is implemented. The liquid-tight shell is designed with a material that inhibits stray currents from propagating through it. This is best achieved by using an electrical insulator. In addition, the material can be selected to be elastic, UV-resistant, temperature-resistant, and tear-resistant as well as resistant to aging. Possible elastomeric materials are chlorosulfonated polyethylene (CSM), ethylene propylene diene monomer (EPDM), fluorocarbon rubber (FKM), or other materials known in the art. The rubber, e.g., EPDM, may contain metal parts, such as nickel parts. Insulating materials may be used for all other components as well, such as pressure ports and ballast elements.

[0033] According to one embodiment of the present invention, the pressure unit is designed to depressurize the expandable closure means by pumping gas out of the cavity through a suction valve in the pressure port.

[0034] Electrolysis units can be constructed in various ways. Typical designs are the atmospheric electrolyser and the pressure stack design electrolyser.

[0035] In one embodiment of the invention, the electrolysis unit is an atmospheric electrolyser and / or a pressurized stack design electrolyser with an internal manifold, and the expandable closure means is located in the fluid manifold system of the atmospheric electrolyser and / or the pressurized stack design electrolyser.

[0036] In atmospheric electrolysers, the individual electrolytic cells are grouped into cell units by placing them next to each other. The manifold system for delivering electrolyte to the cells is external. A main manifold carries the electrolytic medium to the cell units. The main manifold then branches out to the individual cells. The exhaust is also external, via pipes exiting the individual cells.

[0037] Electrolyzers with a pressurized stack design include an internal manifold. One or more electrolysis pipes flow through a pressurized arrangement of several cell components. Electrolyte delivery also occurs through pipes that run through the system.

[0038] The problem of stray and reverse currents occurring when the electrolysis unit is switched off is a common problem. Stray currents occur in both the external and internal manifolds and equally lead to reverse currents in the cells. The structural components of the conduits through which the electrolyte is delivered to the electrolysis unit or into the individual cells are common to both systems and may only differ in size and shape. Advantageously, the expandable closure means can be manufactured and installed in a variety of sizes and lengths. Thus, the expandable closure means is suitable for a variety of electrolyzer designs.

[0039] The present invention further relates to a method for the operation of an electrolysis unit, the method comprising the simultaneous or sequential steps of: feeding an electrolyte into an electrolysis cell through a fluid manifold system having fluid conduits and discharging the electrolyte from the electrolysis cell; and pressurizing an expandable closure means located in the fluid manifold system, the expandable closure means having a liquid-tight shell surrounding a cavity and having a pressure port, the expandable closure means being pressurized through the pressure port using a pressure unit connected to the pressure port until the expandable closure means is in a pressurized state, whereby the liquid-tight shell expands and the volume of the cavity increases, and in the pressurized state the fluid manifold system is closed against the passage of electrolyte.

[0040] The method according to the invention is particularly intended to use an electrolysis unit according to the invention, and therefore has the same advantages as the system according to the invention.

[0041] According to one embodiment of the method, the expandable closure means is pressurized during shutdown of the electrolysis unit.

[0042] According to one embodiment of the method, the cavity of the expandable closure is pressurized with compressed nitrogen or compressed air, which is a cost-effective option for filling the cavity with readily available gases such as nitrogen or air.

[0043] According to one embodiment of the method, the expandable closure means is contracted during operation of the electrolysis unit, thereby creating a reduced pressure state in which the fluid manifold system is open to the passage of electrolyte.

[0044] According to one embodiment of the method, the expandable closure means remains in the fluid conduit during operation of the electrolysis unit. In particular, the expandable closure means is pre-installed.

[0045] Since the expansion and contraction of the expandable closure means must be repeatedly activated and deactivated, it is time-consuming and impractical to install and remove it every time. However, the electrolysis process must not be limited by additional components. The contraction of the expandable closure means and the associated reduction in the volume and blocked cross-section in the conduit make it feasible for the expandable closure means to remain in the fluid conduit without interfering with the electrolysis process. The electrolyte can move freely in the conduit, and the contracted expandable closure means only occupies a small area.

[0046] To enable electrolysis, the electrolysis unit must be energized. If the electrolysis unit needs to be switched off, for example because of lack of solar power overnight, the coatings of the anode and cathode must be protected from residual reverse currents flowing in the fluid manifold system and the fluid conduits. In this case, an overnight shutoff may be performed. In a first step, the polarizing rectifier must remain switched on for several hours to fill the electrolytic cell with cold electrolyte until the temperature at the outlet falls below a specified threshold temperature. The polarizing rectifier can then be switched off and the electrolyte circulation is stopped. From this moment on, stray currents may appear, which lead to reverse currents in the cell and damage the surfaces of the anode and cathode. For this reason, the expandable closure means is activated, i.e. the cavity is pressurized, whereby the expandable closure means is expanded. This means that the expandable closure means is brought into a pressurized state.

[0047] The expandable closure in the fluid manifold system is inflated with sufficient pressure to fully expand within the manifold. The cavity of the expandable closure is filled with pressurized gas through a pressure port until the outer wall of the expandable closure seals against the inner wall of the fluid conduit. This results in hydraulic isolation of the compartments before and after the expandable closure, as electrolyte solution can no longer pass through. In particular, the expandable closure is designed to prevent stray currents when the electrolysis process is interrupted.

[0048] According to yet another configuration of the method, the expandable closure means is depressurized when the electrolytic cell is activated. Thus, the expandable closure means may remain in the system when electrolysis is taking place. Thus, reversible use and fast, uncomplicated switching between pressurized and depressurized states can be achieved. Before resuming the electrolyte flow, the expandable closure means must be deflated. This is done by pumping out the previously injected gas. The same pressure unit and pressure port used for the expansion step can be used for the deflation step. This ensures that the setup remains easy to handle. In particular, the used gas can be collected in a tank and reused if necessary.

[0049] According to one embodiment of the method, the temperature of the electrolyte is measured and, after the electrolyte solution has cooled below a defined temperature, the pressure unit is activated, for example via the control unit, for shutting off the electrolysis unit. The expandable closure means is then expanded until a predefined threshold pressure value is reached. For operation of the electrolysis unit, the expandable closure means is contracted and the electrolysis process is started.

[0050] According to one embodiment of the method, the electrolysis unit is operated with an alkaline water electrolyte.

[0051] In particular, the method is run again at a predefined time, for example with the onset of daylight. [Brief description of the drawings]

[0052] [Figure 1] FIG. 1 is a side view of one embodiment of an electrolysis unit of the present invention. [Diagram 2] FIG. 2 illustrates a cross-section of the fluid manifold system of the embodiment shown in FIG. [Diagram 3] 1 is a flow diagram of one embodiment of a method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Next, an embodiment of the present invention will be described with reference to the drawings.

[0054] An embodiment of an electrolysis unit 20 according to the present invention will be described with reference to Figs. 1 to 3.

[0055] The electrolysis unit 20 is subdivided into individual electrolysis cells 30. Figure 1 depicts only two of these individual electrolysis cells 30. The electrolysis cells 30 are constructed of an anode compartment and a cathode compartment, which are separated by an ion-exchange diaphragm 3. The anode compartment has a liquid chamber bounded by an anode wall 4 on the side opposite the diaphragm 3. Inside the anode compartment there is an anode 1, which is constructed of a substrate made of a mesh or other porous metal structure. In the anode compartment oxygen is produced and expels in the form of gas bubbles in the electrolyte phase. The cathode compartment is a gas chamber bounded by a cathode wall 5 on the side opposite the diaphragm 3. The cathode product is hydrogen.

[0056] A fluid manifold system, including a main conduit 6 and a number of fluid conduits 7, delivers electrolyte into and removes electrolyte from the electrolytic cells 30. The main conduit 6 of the fluid manifold system 6 allows electrolyte to reach the vicinity of the electrolytic cells 30. Smaller fluid conduits 7 branch off from the main conduit 6 and connect to the individual cells 30 to supply them with electrolyte.

[0057] Such an electrolysis unit 20 is known per se. It is designed to electrolyse an alkaline water electrolyte to obtain oxygen and hydrogen. It can be an atmospheric electrolyser or an electrolyser of pressurised stack design including an internal manifold.

[0058] The electrolysis unit according to the present invention comprises an expandable closure means 8 placed in a fluid manifold system as depicted in Figure 1. The expandable closure means 8 has a liquid-tight shell 9 and encloses a cavity 10. It is connected to an external pressure unit 12 via a pressure port 11 and a hose 14. The expandable closure means 8 can be placed in a pressurized state as shown in Figures 1 and 2, as well as in a reduced pressure state as shown in Figure 3.

[0059] Under pressure, a pressure unit 12, which may be a pump, compresses ambient air or nitrogen, which may be stored in an external tank, and supplies it to a pressure port 11 of an expandable closure means 8 in the fluid manifold system via a hose 14. The compressed gas supplied by the pressure unit 12 expands a cavity 10 of the expandable closure means 8 until a liquid-tight shell 9 is pressed against an inner wall of the fluid manifold system. Under pressure, the expandable closure means 8 seals the portion of the fluid manifold system in which it is placed, preventing the electrolyte solution from passing through.

[0060] In the reduced pressure state shown in FIG. 3, the expandable closure means 8 is contracted so that the cross-section of the expandable closure means 8 does not block the electrolyte solution from passing through the fluid manifold system. In this case, no pressure is applied to the inner wall of the fluid-tight shell 9 of the expandable closure means 8. The fluid-tight shell 9 retracts to the relaxed state shown in FIG.

[0061] The material of the liquid-tight shell 9 is elastic, so that it expands under pressure to the pressurized state shown in Figure 2. The liquid-tight shell 9 of the expandable closure means 8 is manufactured from Hypalon. The material of the liquid-tight shell 9 can also be EPDM or other materials that are elastic, UV-resistant, temperature-resistant, and aging-resistant as well as tear-resistant. Additionally, the liquid-tight shell 9 is an electrical insulator.

[0062] The expandable closure means 8 further includes ballast components 13, which are placed within the cavity 10 and attached to the inner surface of the liquid-tight shell 9. Depending on the geometry of the liquid-tight shell 9, the ballast components 13, which are somewhat shorter in length than the expandable closure means 8, may be placed along the length of the expandable closure means 8 as shown in FIG.

[0063] In another embodiment of the present invention, several ballast components 13 may be distributed along the length of the expandable closure means 8 .

[0064] In a pressurized state, the expandable closure means 8 is pressed against the wall of the fluid manifold system so that it cannot be displaced. However, in a reduced pressure state, the expandable closure means 8 may move within the fluid manifold system, for example due to the force of the electrolyte flowing within the fluid manifold system. In this case, the ballast component 13 presses down the expandable closure means 8 and holds them at the bottom of the fluid manifold system. Thus, displacement of the expandable closure means 8 is prevented by the ballast component 13.

[0065] There are several possible arrangements for the placement of the expandable closure means 8 within the fluid manifold system. In one arrangement, the expandable closure means 8 is placed directly in front of the inlet 15 of the electrolysis cell 30. In this case, pressurization of the expandable closure means 8 prevents the passage of electrolyte into the cell 30.

[0066] According to another arrangement, the expandable closure means 8 is placed in the main conduit 6 of the fluid manifold system as shown in Figure 1. In this case, the pressurized state of this expandable closure means 8 may prevent the passage of electrolyte solution into some or all of the fluid conduits 7.

[0067] In another embodiment of the invention, instead of using a ballast component 13, the expandable closure means 8 is fixed to the wall of the fluid manifold system, for example to the lower part of the main conduit 6. In this case, the liquid-tight shell 9 of the expandable closure means 8 is attached longitudinally to the wall of the main conduit 7, for example by adhesive. The fixing is performed in such a way that when inflated, the arrangement of the expandable closure means 8 closes the inlet to the fluid conduit 7, and when deflated, it is neatly arranged at the bottom of the main conduit 7 without randomly collapsing and without disturbing the flow.

[0068] In another embodiment of the invention, the expandable closure means 8 is fixed to the wall of the fluid conduit 7. The fixing is performed in such a way that when inflated, the expandable closure means 8 is arranged to close the inlet 15 of the cell 30 and when deflated, it is spaced from said inlet.

[0069] In another embodiment of the present invention, instead of using a ballast component 13, at least a portion of the shell 9 of the expandable closure means 8 is manufactured from a heavy, non-floating material, which causes the expandable closure means 8 to drop itself to the bottom of the main conduit 6 when uninflated.

[0070] In yet another embodiment of the present invention, the fluid manifold system has an integral chamber in which the contracted expandable closure means 8 is retracted and stored as long as the electrolysis process continues. The chamber is located in or near the pressure port 11. The pressure unit 12 contracts the expandable closure means 8 and creates an additional slight negative pressure. In this way, the expandable closure means 8 can be retracted into the storage chamber and easily pushed out again from the storage chamber upon expansion.

[0071] The electrolysis unit 20 can be put into an active and a deactivated state.

[0072] In the active state, an electric current is applied between the anode 1 and the cathode 2 for the electrolysis process. In this case, the expandable closure means 8 is in a reduced pressure state as shown in Fig. 3. The ballast component 13 holds the contracted expandable closure means 8 in an extended state below the main conduit 6 or fluid conduit 7, which can be passed by the electrolyte.

[0073] In the deactivated state, there is no current. The pressure unit 12 applies pressure to the cavity 10 of the expandable closure means 8, which is then in a pressurized state as shown in FIG. 2. In this case, the electrolyte solution may not pass through the fluid manifold system where the expandable closure means 8 is located. Either the passage of the main conduit 6 is blocked or the passage of one or more fluid conduits 7 is blocked.

[0074] In the following, an embodiment of the method of the invention will be described with reference to Figure 4 and further details of an embodiment of the electrolysis unit 20 will also be described. In particular, the electrolysis unit 20 described above is used in this embodiment of the method of the invention.

[0075] In this method, the electrolysis unit 20 is connected to a solar panel which provides power to the electrolysis unit 20 for electrolysis. The starting point of the method is an active state of the electrolysis unit 20, where oxygen and hydrogen are generated by the power provided by the solar panel. As mentioned before, in this case the expandable closure means 8 is placed in the main conduit 6. However, the expandable closure means 8 is under reduced pressure so that the passage for the electrolyte is not blocked.

[0076] In step S1, the voltage provided by the solar panel is measured. In addition, the temperature of the electrolyte is measured. When the sun goes down, the solar panel cannot be used any more to generate the power required for electrolysis. If a certain drop in the power provided by the solar panel is detected, a shut-down of the electrolysis unit 20 is initiated in step S2. In step S3, the polarization rectifier is left switched on for several hours (2-3 hours) and the electrolysis cells 30 are filled with cold electrolyte solution until the temperature at the discharge header drops from 88°C to 45-50°C. After this, in step S4, the polarization rectifier is switched off and the electrolyte circulation is stopped. When the polarization is switched off, a reverse current can form from stray currents flowing in the fluid manifold system that hydraulically connects all the electrolysis cells 30 of the electrolysis unit 20.

[0077] To avoid such stray currents that could damage the unprotected coatings of the anode 1 and cathode 2, the expandable closure means 8 is pressurized. For this purpose, in step S5, the pressure unit 12 is started, pumping nitrogen, alternatively air, from a tank through a hose 14 into the expandable closure means 8. The liquid-tight shell 9 is inflated, increasing the volume of the cavity 10 and increasing the cross section from a diameter of 25 to a diameter of 60 mm. Sufficient pressure is applied to fully expand the expandable closure means 8 into the main conduit 6 of the fluid manifold system. The inflated expandable closure means 8 blocks the entrance to the fluid conduits 7 that branch off to the individual cells 30. The cells 30 are hydraulically isolated from each other, so that no current can flow through the electrolyte liquid conduits. Any current that could diffuse across the expandable closure means 8 is prevented by using an insulating material for the liquid-tight shell 9.

[0078] When the electrolysis unit 20 is activated again to generate oxygen and hydrogen, the expandable closure means 8 is deflated in step S6 by venting nitrogen through the suction valve of the pressure port 11 connected to the pressure unit 12. The expandable closure means 8 shrinks again to its original size with a smaller cross section and volume. During the active electrolysis process, this deflated shell 9 of the expandable closure means 8 remains in the fluid manifold system. The ballast component 13 ensures that the deflated shell remains at the bottom of the fluid manifold system, e.g. the bottom of the main conduit 6, without being drifted away by the electrolyte solution flowing around it.

[0079] In another embodiment, several expandable closure means 8 are used, which are pre-installed in the fluid conduits 7 leading from the main conduit 6 of the fluid manifold system to the individual cells 30. The material and structure of the liquid-tight shell 9 are identical to those described in the first embodiment. However, the expandable closure means 8 provide a smaller cross-section adapted to the thinner conduits. The pressure ports 11 of the individual closure means 8 are connected via a valve system, allowing all the expandable closure means 8 to be controlled simultaneously via one external pressure unit 12.

[0080] The liquid-tight shells 9 of some of the expandable closure means 8 are expanded, increasing the volume of the cavities 10. Sufficient pressure is applied to expand the expandable closure means 8 completely into the fluid conduits 7. The expanded expandable closure means 8 blocks all of the individual fluid conduits 7. The electrolysis cells 30 are hydraulically isolated from one another, and therefore no electrical current can flow in the electrolyte liquid conduits. Any electrical current that may diffuse across the expandable closure means 8 is prevented by the use of insulating materials.

[0081] Before resuming electrolyte flow in anticipation of re-energizing the electrolysis unit 20, the expandable closure means 8 are deflated by venting nitrogen. The pressure unit 12 depressurizes the expandable closure means 8. The pressure unit 12 pumps compressed nitrogen back through the return valve of the pressure port. The expandable closure means 8 contract again to their original size of smaller cross section and volume. The ballast component 13 ensures that the expandable closure means 8 remain in the fluid conduit 7. [Explanation of symbols]

[0082] 1 Anode 2 Cathode 3. Ion exchange membrane 4 Anode Wall 5 Cathode wall 6 Main conduit 7 Fluid conduit 8 Expandable Closure Means 9 Liquid-tight shell 10 Cavity 11 Pressure port 12 Pressure Unit 13 Ballast Components 14 Hose 15 Entrance 20 Electrolysis Unit 30 Electrolysis Cell

Claims

1. a plurality of electrolysis cells (30), each having an anode (1), a cathode (2), and an ion exchange membrane (3) dividing the electrolysis cell (30) into an anode compartment and a cathode compartment; a fluid manifold system (6, 7) having fluid conduits (7) for feeding electrolyte into the electrolytic cell (30) and for discharging electrolyte from the electrolytic cell (30); an expandable closure means (8) having a fluid-tight shell (9) surrounding a cavity (10), said fluid-tight shell (9) having a pressure port (11); a pressure unit (12) connected to the pressure port (11) for pressurizing the cavity (10) so that the liquid-tight shell (9) expands and the volume of the cavity (10) increases; An electrolysis unit (20) comprising: the expandable closure means (8) is disposed within a fluid manifold system (6, 7) such that when the expandable closure means (8) is in a decompressed state, the fluid manifold system (6, 7) is open to the passage of electrolyte, and when the expandable closure means (8) is in a pressurized state, the fluid manifold system (6, 7) is closed to the passage of electrolyte; The expandable closure means (8) includes a ballast component (13) that holds the expandable closure means (8) at a reduced pressure at the bottom of the fluid manifold system (6, 7). Electrolysis unit (20).

2. 2. The electrolysis unit (20) of claim 1, wherein at least one fluid conduit (7) provides a fluid connection from one electrolysis cell (30) to another electrolysis cell (30).

3. 3. The electrolysis unit (20) according to claim 2, wherein an expandable closure means (8) is arranged in at least one of the fluid conduits (7) directly in front of the inlet (15) of one of the electrolysis cells (30).

4. 2. The electrolysis unit (20) of claim 1, wherein the fluid manifold system (6, 7) comprises a main conduit (6) from which at least one fluid conduit (7) branches, and wherein the expandable closure means (8) is disposed in the main conduit (6).

5. Electrolysis unit (20) according to claim 1, wherein the liquid-tight shell (9) of the expandable closure means (8) is an electrical insulator.

6. 2. The electrolysis unit (20) according to claim 1, wherein the pressure unit (12) is designed to depressurize the expandable closure means (8) by pumping gas out of the cavity (10) through a return valve of the pressure port (11).

7. 7. The electrolysis unit (20) according to any one of claims 1 to 6, wherein the electrolysis unit is an atmospheric electrolyzer and / or a pressurized stack design electrolyzer including an internal manifold, and wherein the expandable closure means (8) is located in the fluid manifold system (6, 7) of the atmospheric electrolyzer and / or the pressurized stack design electrolyzer.

8. A method for the operation of an electrolysis unit (20) comprising the simultaneous or sequential steps of: feeding the electrolyte into the electrolytic cell (30) through a fluid manifold system (6, 7) having fluid conduits (7) and discharging the electrolyte from the electrolytic cell (30); pressurizing an expandable closure means (8) placed in a fluid manifold system (6, 7), said expandable closure means (8) having a liquid-tight shell (9) surrounding a cavity (10) and having a pressure port (11), applying pressure through the pressure port (11) using a pressure unit (12) connected to the pressure port (11) until the expandable closure means (8) is in a pressurized state, thereby causing the liquid-tight shell (9) to expand and increasing the volume of the cavity (10), and in the pressurized state the fluid manifold system (6, 7) is closed to the passage of electrolyte; Including, the expandable closure means (8) is contracted during operation of the electrolysis unit (20), thereby creating a vacuum state in which the fluid manifold system (6, 7) is open to the passage of electrolyte; The expandable closure means (8) includes a ballast component (13) that holds the expandable closure means (8) at a reduced pressure at the bottom of the fluid manifold system (6, 7). method.

9. 9. The method according to claim 8, wherein the expandable closure means (8) is pressurized during shutdown of the electrolysis unit (20).

10. 10. The method according to claim 8 or 9, wherein the cavity (10) of the expandable closure means (8) is pressurized with compressed nitrogen or compressed air.

11. 9. The method of claim 8, wherein the expandable closure means (8) remains in the fluid conduit (7) during operation of the electrolysis unit (20).

12. The temperature of the electrolyte is measured, The pressure unit (12) is activated after the electrolyte solution has cooled below a predetermined temperature to shut off the electrolysis unit (20); Inflating the expandable closure means (8) until a predetermined threshold pressure value is reached; Contracting the expandable closure means (8) for operation of the electrolysis unit (20); The electrolysis process begins, 12. The method of claim 8 or 11.

13. 9. The method of claim 8, wherein the electrolysis unit (20) is operated with alkaline water electrolyte.

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